1. Field of the Invention
This invention relates to an optical fiber material comprising an optical fiber and a wrapping material wrapping at least a part of the peripheral surface of the optical fiber in the axial direction of the optical fiber, a process for its production and a device or tool for its production.
2. Description of the Prior Art
Optical fibers made of such a material as quartz, multi-component glass or synthetic resins are known. Because of their generally very small diameter, they are susceptible to permanent deformation when undergoing a force exerted in a direction at right angles to the fiber axis. For example, optical fibers made of quartz or multi-component glass are liable to break, and those made of synthetic resins are liable to bend or break, under such a force.
Generally, the optical fibers are protected by flexible plastic primary coats to avoid permanent deformation (such as breaking or bending) during processing and handling or in the process of distribution to end users or to prevent them from becoming fragile upon being hydrolyzed by adhering water.
However, under conditions encountered in actual use where the optical fibers frequently undergo a relatively large external force, the above plastic primary coats are not so strong as to ensure accurate prevention of permanent deformation. Since such a plastic coat generally has a large clearance from the optical fiber, and a slip agent such as a silicone exists in the clearance, it cannot fix the optical fiber under a large force exerted in the axial direction of the fiber and permits the optical fiber to get out of place.
In protecting an optical fiber from a relatively large exterior force or fix it against an external force, it has been the previous practice to cover it with a ferrule. For example, an optical connector plug is produced by providing a ferrule having a passage formed by high-precision boring at its central part and an outer configuration conforming to the optical connector plug, inserting an optical fiber into the passage of the ferrule, and fixing it with an adhesive. The passage of the ferrule is bored with a high precision so that it conforms as much as possible to the outer configuration of the optical fiber. But for insertion of the optical fiber, the passage should be larger than the outside dimension of the optical fiber, and the use of an adhesive is essential to the fixation of the optical fiber.
The fixing of optical fibers by ferrules in the prior art has the defect that the use of adhesives complicates the process steps, a long period of time is required for the solidification of the adhesives, and the yield of the product is poor.